This invention relates to systems for aerating lakes and ponds, as well as to equipment for use in such systems.
Many bodies of water that are used for recreational or water supply purposes (e.g., lakes, ponds, rivers, lagoons, bays, or reservoirs) often become eutrophic, a condition characterized by an abundant accumulation of nutrients that support a dense growth of plant and animal life, the decay of which releases nitrogen and phosphorus, depleting the waters of oxygen. For convenience herein, in both the description of the invention and the claims that define it, all such bodies of water will be deemed to be included in the term "lakes."
There are many commercial pieces of equipment that aerate or oxygenate eutrophic lakes by supplying air from a land-based compressor to an air release location on the lake bottom, where the air is allowed to bubble to the surface of the water. In currently preferred systems, the air is transmitted through a hose to a diffuser positioned on the floor of the lake, where small bubbles are released and rise to the surface, creating turbulent, or preferably laminar, flow of the water. This aeration helps rejuvenate lakes by eliminating algae, oxidizing debris on the lake bottom, and helps restore the lake to usable condition.
Prior to the present invention, many attempts have been made to find a suitable air transport hose, which must be heavy enough to stay submerged when filled with air, capable of resisting snagging on fishing lines or the propellers of outboard motors, and desirably possess rodent repellence. One commercially used hose has been a high density rubber that has an outside diameter (o.d.) of 15/16 inch (about 24 mm) and an inside diameter (i.d.) of 9/16 inch (about 14 mm), preferably treated with muskrat repellent. This hose is bulky, expensive, susceptible to snagging, and has a high coefficient of friction with respect to the air passing through it.
Another commercially used hose is a vinyl tube having an o.d. of about 15 mm and an i.d. of about 12.5 mm, along the length of which is attached a vinyl-encased lead wire. Although having a low coefficient of friction with respect to the transported air, this type of hose is susceptible to kinking, which may go undetected, thus reducing the ability of air to pass through it. Further, lead is an undesirable--even illegal in some parts of the country--metal to be placed in a lake. It is also believed that the vinyl sheath may be appealing to the muskrats that inhabit many lakes and streams, increasing the possibility that the lead may become exposed and dissolve in the water.
Still another technique has been to use tubing made of high density polyethylene or unplasticized polyvinyl chloride for air transport, attaching brick weights at intervals along its length. This type of arrangement is labor intensive, and since the bricks become entrapped in the sediment on the bottom of the lake, it is difficult to move or replace the hose. Further, the hose itself is potentially susceptible to rodent attack.